JP7002227B2 - Air conditioner - Google Patents

Description

The present invention relates to an air conditioner, and more particularly to a multi-air conditioner characterized by expansion valve control after the compressor is stopped.

It is known that the distribution of refrigerant in the air conditioner differs greatly between when it is in operation and when it is stopped. FIG. 6 is an example of the distribution of the refrigerant inside the air conditioner, and the inside of the air conditioner is roughly divided into four categories: connecting liquid pipe, connecting gas pipe, outdoor unit, and other four categories, and is in operation and stopped (from stop). This is a comparison of the refrigerant distributions after a lapse of a predetermined time). From this, it can be seen that the amount of refrigerant in the connecting liquid pipe and the outdoor unit decreases, and the amount of refrigerant in the connecting gas pipe increases during the stop compared to during operation.

Of particular note is the significant change in the amount of refrigerant held in the connecting liquid pipe. In the example of FIG. 6, the refrigerant in the connecting liquid pipe, which accounted for about 60% during operation, became about 40% when stopped. Has decreased to. This is because most of the refrigerant in the connecting liquid pipe has moved to the connecting gas pipe.

As shown in FIG. 6, if the refrigerant moves from the connecting liquid pipe to the connecting gas pipe while stopped, the refrigerant moving to the connecting gas pipe will move to the connecting liquid pipe the next time the air conditioner is started. There is a problem that it is necessary to move and wait for an appropriate amount of refrigerant to be accumulated again in the connecting liquid pipe, and it takes time to start up the air conditioner.

Further, when the refrigerant moves from the connecting liquid pipe to the outdoor unit, the refrigerant may accumulate in the connecting gas pipe, the accumulator, or the like. When restarting in the state where this accumulation occurs, the risk of liquid compression of the compressor increases, so it is necessary to avoid the risk of liquid compression by increasing the volume of the accumulator.

An object of the present invention is to suppress the movement of the refrigerant from the stopped connecting liquid pipe, thereby shortening the time required for restarting, improving comfort and reliability, and manufacturing cost due to the increase in size of the accumulator. The purpose is to provide an air conditioner that prevents the increase.

In order to solve the above problems, the air conditioner of the present invention includes an outdoor unit having a compressor, an outdoor heat exchanger and an outdoor expansion valve, an indoor heat exchanger, an indoor unit having an indoor expansion valve, and the outdoor unit. A liquid pipe connecting the indoor unit and a gas pipe connecting the outdoor unit and the indoor unit is provided, and one end of the outdoor heat exchanger is connected to the liquid pipe via the outdoor expansion valve. One end of the indoor heat exchanger is connected to the liquid pipe via the indoor expansion valve, and both the outdoor expansion valve and the indoor expansion valve are closed after a predetermined time has elapsed from the stop of the compressor. did.

Further, other air conditioners of the present invention include an outdoor unit having a compressor, an outdoor heat exchanger and an outdoor expansion valve, an indoor heat exchanger, an indoor unit having an indoor expansion valve, and a high / low pressure gas pipe switching valve. A cooling / heating switching unit having a low-pressure gas pipe switching valve, a liquid pipe connecting the outdoor unit and the indoor unit, a high-low pressure gas pipe connecting the outdoor unit and the high-low pressure gas pipe switching valve, and the outdoor unit. A low-pressure gas pipe connecting the low-pressure gas pipe switching valve and a gas pipe connecting the indoor unit and the cooling / heating switching unit are provided, and one end of the outdoor heat exchanger is the liquid pipe via the outdoor expansion valve. One end of the indoor heat exchanger is connected to the liquid pipe via the indoor expansion valve, and after a predetermined time has elapsed from the shutdown of the compressor, both the outdoor expansion valve and the indoor expansion valve Or close all of the outdoor expansion valve, the high / low pressure gas pipe switching valve, and the low pressure gas pipe switching valve.

Further, other air conditioners of the present invention include a compressor, an outdoor heat exchanger, an outdoor unit having an outdoor expansion valve, an indoor heat exchanger, an indoor unit having an indoor expansion valve, a gas-liquid separator, and a high-pressure pipe. A cooling / heating switching unit having a switching valve, a switching valve for a low pressure pipe, and a hydraulic pressure adjusting expansion valve, a high pressure pipe connecting the outdoor unit and the cooling / heating switching unit, and a low pressure pipe connecting the outdoor unit and the cooling / heating switching unit. A gas pipe connecting the indoor unit and the cooling / heating switching unit, and a liquid pipe connecting the indoor unit and the cooling / heating switching unit are provided, and one end of the outdoor heat exchanger has the high pressure via the outdoor expansion valve. One end of the indoor heat exchanger is connected to the liquid pipe via the indoor expansion valve, and after a predetermined time has elapsed from the shutdown of the compressor, the outdoor expansion valve, the indoor expansion valve, and the like. The switching valve for the high pressure pipe, the switching valve for the low pressure pipe, and the hydraulic pressure adjusting valve are all closed.

According to the present invention, since the movement of the refrigerant from the connecting liquid pipe at the time of stopping can be suppressed, the start-up of the heating operation or the cooling operation at the time of restarting the air conditioner can be accelerated, and the comfort can be improved. .. Further, since the possibility of liquid compression in the compressor can be reduced without increasing the size of the accumulator, the reliability can be improved without increasing the manufacturing cost.

Conventional expansion valve control when heating is stopped in the cooling / heating switching multi Conventional expansion valve control when cooling is stopped in the cooling / heating switching multi Expansion valve control at the time of stop of Example 1 in the cooling / heating switching multi Example of refrigerant differential pressure due to height difference Example of refrigerant differential pressure due to indoor / outdoor temperature difference An example of refrigerant distribution during operation and stop Isochoric change of liquid refrigerant Pressure behavior during stop from conventional operation Pressure behavior during stop from operation during stop expansion valve control Pressure behavior during stop from operation during stop expansion valve control Flow chart example of expansion valve control when stopped Conventional stop expansion valve control in simultaneous cooling and heating multi Expansion valve control when stopped in Example 2 in simultaneous cooling and heating multi Expansion valve control at the time of stop of the modified example of Example 2 in the simultaneous cooling / heating multi (cooling / heating switching unit valve open) Expansion valve control at the time of stop of another modification of Example 2 in the simultaneous cooling and heating multi (heating chamber expansion valve open) Conventional expansion valve control at stop in 2-tube cooling / heating simultaneous multi Expansion valve control when stopped in Example 3 in a two-tube cooling / heating simultaneous multi Expansion valve control when cooling is stopped according to the fourth embodiment in the configuration using a supercooling circuit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the air conditioner according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 5 and 7 to 11.
<Conventional expansion valve control when heating is stopped>
FIG. 1 is a refrigeration cycle system diagram showing conventional expansion valve control when heating is stopped, which is applied to the air conditioner 100 of the cooling / heating switching multi. The air conditioner 100 shown here is a device in which an outdoor unit 10 and an indoor unit 40 (general term for 40a, 40b, 40c, 40d) are connected by a liquid main pipe 21 and a gas main pipe 24, and each indoor unit 40 is heated. It is in a stopped state. Although FIG. 1 illustrates a configuration in which one outdoor unit 10 and four indoor units 40 are used, a configuration other than this may be used.

The indoor unit 40a is composed of an indoor heat exchanger 41a, an indoor expansion valve 42a, and an indoor heat exchanger fan 49a. Then, one end of the indoor heat exchanger 41 communicates with the liquid main pipe 21 via the indoor expansion valve 42. Further, an indoor heat exchanger gas temperature sensor 45a, an indoor heat exchanger liquid temperature sensor 46a, and an indoor heat exchanger 73a are installed at the locations shown in the figure. Since the configurations of the indoor units 40b, 40c, and 40d are the same, duplicate description will be omitted.

The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger fan 13, an outdoor heat exchanger 14, an outdoor expansion valve 15, a compressor check valve 16, and an accumulator 18. Then, one end of the outdoor heat exchanger 14 communicates with the liquid main pipe 21 via the outdoor expansion valve 15. Further, a discharge pressure detection sensor 55, an outdoor heat exchanger liquid temperature sensor 50, an outdoor heat exchanger gas temperature sensor 51, a liquid pressure detection device 71, and an outside air temperature sensor 72 are installed at the locations shown in the figure.

Next, the flow of the refrigerant during the heating operation and when the heating is stopped will be described. During the heating operation, the high-temperature high-pressure gas refrigerant compressed by the compressor 11 is sent to the indoor unit 40 via the four-way valve 12 and the gas main pipe 24.

In the indoor unit 40, the gas refrigerant flowing into the indoor heat exchanger 41 exchanges heat with the indoor air and condenses to become a high-pressure two-phase refrigerant or a high-pressure overcooling refrigerant, via the indoor expansion valve 42 and the liquid main pipe 21. It is sent to the outdoor unit 10.

In the outdoor unit 10, the flow rate of the inflowing refrigerant is adjusted by the outdoor expansion valve 15 opened at a desired opening degree, heat is exchanged with the outdoor air by the outdoor heat exchanger 14, and the refrigerant evaporates to become a low-pressure gas refrigerant. It is sent to the compressor 11 via the four-way valve 12 and the accumulator 18, and the refrigeration cycle during the heating operation is completed. During this heating operation, the inside of the liquid main pipe 21 is almost filled with the liquid refrigerant, and only the gas refrigerant is present in the gas main pipe 24.

When the heating is stopped from here, as shown in FIG. 1, the outdoor expansion valve 15 is fully closed and the indoor expansion valve 42 is open. Immediately after the compressor 11 is stopped, the pressure of the gas main pipe 24 downstream thereof decreases, and after a certain period of time, it balances with the suction side pressure of the compressor 11. When this balance pressure becomes lower than the pressure of the liquid main pipe 21, the liquid refrigerant in the liquid main pipe 21 moves to the gas main pipe 24 through the indoor expansion valve 42 and the indoor heat exchanger 41, and the refrigerant moves as shown in FIG. Occurs. Further, since the four-way valve 12 and the compressor check valve 16 are not completely sealed, the refrigerant in the gas main pipe 24 may move to the accumulator 18 and the outdoor heat exchanger 14. In this way, if the refrigerant in the liquid main pipe 21 is dispersed in various parts of the refrigeration cycle, the operation efficiency is poor and it takes time to start heating until the refrigerant is properly distributed to each part of the refrigeration cycle at the next start-up. It ends up.

Further, when the refrigerant is accumulated in the outdoor heat exchanger 14 after the heating operation is stopped, the refrigerant in the gas-liquid mixed state enters the accumulator 18 at the time of starting. The accumulator 18 separates the liquid refrigerant from the low-pressure refrigerant in the gas-liquid mixed state and sends the gas refrigerant to the compressor 11 to prevent the liquid compression of the compressor 11, but the liquid returns from the outdoor heat exchanger 14. If the amount is large, or if the refrigerant is accumulated in the accumulator 18 itself, the function of separating the liquid refrigerant is lowered, and the risk of liquid compression of the compressor is increased. In order to prevent this, it is necessary to increase the volume of the accumulator 18, which increases the manufacturing cost.
<Conventional expansion valve control when cooling is stopped>
FIG. 2 is a refrigeration cycle system diagram showing the conventional expansion valve control at the time of cooling stop applied to the air conditioner 100 having the same configuration as that of FIG. 1, and the connection of the four-way valve 12 is different from that of FIG. Using this figure, the flow of the refrigerant during the cooling operation and during the cooling stop will be described. During the cooling operation, the high-temperature high-pressure gas refrigerant compressed by the compressor 11 is sent to the outdoor heat exchanger 14 via the four-way valve 12. The gas refrigerant flowing into the outdoor heat exchanger 14 exchanges heat with the outdoor air and condenses to become a high-pressure two-phase refrigerant or a high-pressure overcooling refrigerant, which is sent to the indoor unit 40 via the outdoor expansion valve 15 and the liquid main pipe 21. Be done. In the indoor unit 40, the flow rate of the inflowing refrigerant is adjusted by the indoor expansion valve 42 opened at a desired opening, and the indoor heat exchanger 41 exchanges heat with the indoor air to evaporate and becomes a low-pressure gas refrigerant. It is sent to the compressor 11 via the gas main pipe 24, the four-way valve 12, and the accumulator 18, and the refrigeration cycle during the cooling operation is completed. During this cooling operation, the inside of the liquid main pipe 21 is almost filled with the liquid refrigerant, and only the gas refrigerant is present in the gas main pipe 24.

When the cooling is stopped from here, the indoor expansion valve 42 is fully closed and the outdoor expansion valve 15 is opened, as shown in FIG. Immediately after the compressor 11 is stopped, the pressure of the outdoor heat exchanger 14 drops, and after a certain period of time, it balances with the suction side pressure of the compressor 11. When this balance pressure becomes lower than the pressure of the liquid main pipe 21, the refrigerant of the liquid main pipe 21 moves to the outdoor heat exchanger 14 through the outdoor expansion valve 15, so that the refrigerant movement shown in FIG. 6 occurs. Further, since the four-way valve 12 and the compressor check valve 16 are not completely sealed, the refrigerant in the outdoor heat exchanger 14 may move to the accumulator 18 and the gas main pipe 24. In this way, if the refrigerant in the liquid main pipe 21 is dispersed in various parts of the refrigeration cycle, the cooling efficiency is poor and it takes time to start cooling until the refrigerant is properly distributed to each part of the refrigeration cycle at the next start-up. It ends up.

Further, if the refrigerant accumulates in the gas main pipe 24 after the cooling operation is stopped, the amount of liquid returned at the time of starting increases, the liquid-refrigerant separation function of the accumulator 18 deteriorates, and the risk of compressor liquid compression increases. In order to prevent this, it is necessary to increase the volume of the accumulator 18, which increases the manufacturing cost.
<Control of expansion valve when stopped in Example 1>
FIG. 3 is a refrigeration cycle system diagram showing stop-time expansion valve control of the first embodiment applied to the air conditioner 100 having the same configuration as that of FIGS. 1 and 2. Here, the situation where the four-way valve 12 is connected during the cooling operation (FIG. 2) is illustrated, but even if the situation is the connection during the heating operation (FIG. 1), the present embodiment is stopped. Time expansion valve control can be applied.

In this embodiment, when the cooling operation is shifted to the cooling stop, all the indoor expansion valves 42 and the outdoor expansion valves 15 are closed as shown in FIG. As described above, in the conventional expansion valve control at the time of stop, when the compressor 11 is stopped and the pressure on the outflow side of the compressor 11 is reduced, the refrigerant is dispersed in various parts of the refrigeration cycle via the opened expansion valve. However, by closing the expansion valves at both ends of the liquid main pipe 21 together as in this embodiment, it is possible to prevent the liquid refrigerant accumulated in the liquid main pipe 21 from moving to another place during operation, and the next time. It is possible to accelerate the start-up of cooling operation or heating operation at startup.

Next, the liquid refrigerant movement due to the refrigerant differential pressure between the outdoor unit 10 and the indoor unit 40 and the countermeasures thereof will be described with reference to the schematic views of FIGS. 4 and 5.

FIG. 4 is a schematic view of the air conditioner 100 in which the outdoor unit 10 is arranged below and the indoor unit 40 is arranged 10 m above the indoor unit 40 when the cooling operation is stopped. This is an example of how easy it is to move to a heat exchanger. Note that FIG. 4 is also a schematic view of an air conditioner in which the indoor unit 40 is arranged below and the outdoor unit 10 is arranged above the indoor unit 40 when the heating operation is stopped, as shown in parentheses in the figure.

When the lower expansion valve is opened after the cooling operation is stopped, the liquid refrigerant moves to the lower heat exchanger due to the influence of the head of the liquid column. For example, when the height difference between the outdoor unit 10 and the indoor unit 40 is 10 m, the liquid density of the refrigerant is 1000 kg / m ³ , and the outdoor expansion valve 15 is open, the outdoor expansion valve 15 installed at the lower end of the liquid main pipe 21 may be used. A differential pressure of about 0.1 MPa is generated, and the refrigerant in the liquid main pipe 21 moves downward. To prevent this, it is necessary to close the expansion valve on the lower side when stopped, as in this embodiment. Specifically, when the outdoor unit 10 is down and the indoor unit 40 is up, the outdoor expansion valve 15 is closed, and when the outdoor unit 10 is up and the indoor unit is down, the indoor expansion valve 42 is closed. In this way, when there is a height difference between the installation locations of the outdoor unit 10 and the indoor unit 40, it is possible to prevent the inflow of the liquid refrigerant into the lower heat exchanger or the like by closing the lower expansion valve when the operation is stopped. ..

FIG. 5 is a schematic diagram of the air conditioner 100 in which the outdoor unit 10 is arranged in an atmosphere of 17 ° C. and the indoor unit 40 is arranged in an atmosphere of 20 ° C. when the operation of the air conditioner 100 is stopped, and the temperature difference between both ends of the liquid main pipe 21. This is an example in which the refrigerant easily moves to the heat exchanger on the low temperature side. In FIG. 5, it is assumed that the outdoor unit 10 and the indoor unit 40 are set at the same height, and the liquid main pipe 21 is horizontal.

If there is a difference in the temperature of the atmosphere inside and outside the room even when the operation is stopped, heat exchange occurs between the refrigerant inside the air conditioner 100 and the air due to natural convection, and the refrigerant moves. For example, when the temperature is 17 ° C. outdoors and 20 ° C. indoors, it takes time, but the liquid refrigerant in the indoor heat exchanger 41 evaporates and the gas refrigerant in the outdoor heat exchanger 14 condenses, so that the indoor unit 40 The liquid refrigerant of No. 1 gradually accumulates in the outdoor unit 10. Since the saturation pressure at 20 ° C. is 1.45 MPa and the saturation pressure at 17 ° C. is 1.35 MPa, the differential pressure of the saturation pressure due to the indoor / outdoor temperature difference of 3 ° C. shown in FIG. 5 is 0.1 MPa. This corresponds to the liquid transporting force with a height difference of 10 m shown in FIG. 4, and cannot be ignored. Therefore, in order to prevent the outflow of the refrigerant from the liquid main pipe 21 when the temperature difference between the inside and outside of the room exceeds a predetermined value, control may be performed to close the expansion valve on the low temperature side.

FIG. 7 is an image diagram of a liquid sealing phenomenon in which the liquid pipe is filled with the liquid refrigerant. If the temperature is raised after sealing the valves at both ends of the pipe in a full state, the pressure of the liquid refrigerant rises, and if the pressure resistance of the pipe is exceeded, the pipe may be damaged and the refrigerant may leak. Therefore, as shown in FIG. 3, when closing both the indoor expansion valve 42 and the outdoor expansion valve 15 at both ends of the liquid main pipe 21, the valves at both ends are closed after confirming that the liquid main pipe 21 is not full. Is desirable. For example, in the case of heating operation, the degree of overcooling at the outlet of each indoor heat exchanger 41 is detected by the discharge pressure detection sensor 55 and the indoor heat exchanger liquid temperature sensor 46, and the outlet temperatures of all the indoor units 40 are saturated temperatures. In this case, since the two-phase refrigerant is sent to the liquid main pipe 21 and there is a high possibility that the liquid is not full, there is no problem even if the valves at both ends are closed as they are. In addition, if the heat exchanger that becomes the condenser in the height difference construction is underneath, or if the pipe length of the liquid main pipe 21 is long, the pressure drops at the end of the liquid pipe and there is a high possibility that it will become a two-phase refrigerant. There is no problem even if the valves at both ends are closed according to the refrigerant condition. Whether or not the inside of the liquid main pipe 21 is a two-phase refrigerant may be estimated from the cycle state immediately before the stop, the liquid pipe temperature, and the liquid pipe pressure.

FIG. 8 shows the pressure behavior when the conventional stop expansion valve control shown in FIGS. 1 and 2 is performed. When the air conditioner 100 stops operating, the discharge pressure and the suction pressure are gradually balanced so as to be the same pressure. At this time, since the valve at one end of the liquid main pipe 21 is open, the liquid pressure is lower than or almost the same as the discharge pressure. Here, when the discharge pressure becomes lower than the liquid pressure, the refrigerant in the liquid main pipe 21 moves to another device and the pressure naturally drops. As a result, various problems introduced in the explanations of FIGS. 1 and 2 occur.

FIG. 9 shows the pressure behavior when the expansion valve closing control at the time of stop of this embodiment is performed, which is shown in FIG. Similar to FIG. 8, the discharge pressure becomes lower than the liquid pressure shortly after the air conditioner 100 is stopped, but here, since the valves at both ends of the liquid main pipe 21 are closed after the air conditioner 100 is stopped, the liquid main pipe is closed. The liquid pressure in 21 is kept constant.

If the expansion valves at both ends of the liquid main pipe 21 are closed immediately after the air conditioner 100 is stopped, the liquid pressure is maintained in a high state, but this is affected by the influence of the liquid head having a height difference and the influence of the rise in the liquid pipe atmosphere temperature. In order to avoid the risk that the hydraulic pressure will rise due to the addition of water and exceed the pressure resistance of the liquid main pipe 21, the liquid pressure at the initial stop will be increased by closing the expansion valves at both ends of the liquid main pipe 21 for a while after stopping, for example, about a few minutes. It is possible to reduce the risk of damage to the liquid main pipe 21 due to lowering and increasing the liquid pressure.

FIG. 10 shows the pressure behavior when the expansion valve closing control at the time of stopping is performed, and is an example when the outside air temperature and the liquid refrigerant temperature rise for a longer time lapse than in FIG. If it is not liquid-sealed, the liquid pressure rises at a pressure equivalent to the saturation pressure as the temperature rises during the day. If the liquid pressure rises excessively in the liquid main pipe 21 in the liquid sealed state, the liquid main pipe 21 may be damaged. Therefore, the liquid pipe temperature observed by the outdoor heat exchanger liquid temperature sensor 50 or attached to the liquid main pipe 21. When the liquid pressure observed by the liquid pressure detecting device 71 exceeds a predetermined threshold value, the closed expansion valve is temporarily opened to let the liquid fluid of the liquid main pipe 21 escape to another device, thereby causing the inside of the liquid main pipe 21. You may reduce the pressure of. Here, the liquid pressure detecting device 71 may be a pressure sensor that measures the pressure, or may be something like a pressure switch that generates an output when a predetermined pressure is exceeded. In the case of the pressure sensor, since the pressure is measured, the expansion valve may be closed again when the pressure drops below a predetermined value. In the case of a pressure switch, the expansion valve may be closed again after a predetermined time from the time of operation.

Next, the flowchart of the expansion valve control at the time of stop used in this Example will be described with reference to FIG. Since the stop expansion valve control shown here is the control after the air conditioner 100 is stopped, the expansion valve control during the operation of the air conditioner 100 is omitted.

First, in step S1, it is confirmed whether the air conditioner 100 is operating or stopped. If it was in operation, step S1 is repeated until it stops.

In step S2, it is confirmed whether a predetermined time has elapsed since the air conditioner 100 was stopped. Before the lapse of a predetermined time, the process proceeds to step S5, and expansion valve control at a normal stop opening, that is, expansion in which one of the expansion valves at both ends of the liquid main pipe 21 is closed and the other is not closed as shown in FIG. 1 or FIG. Perform valve control. It should be noted that in step S2, the elapse of the predetermined period is confirmed to some extent because the high liquid pressure during operation is maintained when the expansion valve control at the time of stop of the present embodiment shown in FIG. 3 is performed immediately after the stop. This is because it is desirable to execute the stop expansion valve control of this embodiment after the time has elapsed and the liquid pressure in the liquid main pipe 21 has dropped to some extent.

When the passage of the predetermined time is confirmed in step S2, the process proceeds to step S3, and it is confirmed whether the liquid pressure in the liquid main pipe 21 is equal to or less than the predetermined value. If the liquid pressure is higher than the predetermined value, the process proceeds to step S5, and the expansion valve control at the normal stop opening degree is executed. The threshold value used here is determined in consideration of the pressure resistance of the liquid main pipe 21, and by setting this threshold value lower than the pressure resistance of the liquid main pipe 21, the expansion valve at the time of stop of this embodiment is set. Even when the liquid pressure of the liquid main pipe 21 rises due to an increase in the outside air temperature or the like after the execution of the control, it is possible to avoid damage to the liquid main pipe 21. For example, when the withstand voltage of the liquid main pipe 21 is 4 MPa, the threshold value can be 2 MPa, which is half of the withstand voltage.

When it is confirmed in step S3 that the liquid pressure of the liquid main pipe 21 is equal to or less than a predetermined value, the process proceeds to step S4, and it is confirmed whether the liquid main pipe 21 is in a liquid sealed state. When the liquid is sealed, the liquid pressure of the liquid main pipe 21 may rise significantly as shown in FIG. 7 due to an increase in the outside air temperature or the like after the execution of the expansion valve control at the stop of this embodiment. Therefore, the process proceeds to step S5, and the expansion valve control at the normal stop opening degree is executed. Whether or not the liquid is sealed can be determined by checking the presence or absence of gas refrigerant in the liquid main pipe 21, but the height difference construction, pipe length, indoor heat exchanger outlet liquid temperature and overcooling degree during heating operation, and cooling operation It may be judged comprehensively from the liquid pipe temperature, the degree of supercooling, the stopped outside air temperature, the liquid refrigerant temperature, and the like.

If it is determined in step S4 that the liquid is not sealed, the stop expansion valve control of this embodiment as illustrated in FIG. 3 is performed. As a result, when the expansion valves at both ends of the liquid main pipe 21 are closed, it is possible to prevent the refrigerant in the liquid main pipe 21 from flowing out to other elements while avoiding damage to the liquid main pipe 21 due to an increase in the liquid pressure.

Even if the expansion valve control at the time of stop in step S6 is started, if it is necessary to deal with the increase in the hydraulic pressure due to the increase in the outside air temperature as shown in FIG. 10, the expansion due to the normal stop opening in step S5 is performed again. The valve control may be returned, and then, if the hydraulic pressure drops again, the stop expansion valve control in step S6 may be executed.

According to the present embodiment described above, since the movement of the refrigerant from the liquid main pipe to other elements when the operation of the air conditioner is stopped can be suppressed, the start-up of the heating operation or the cooling operation when the air conditioner is restarted is accelerated. And can improve comfort. Further, since the possibility of liquid compression in the compressor can be reduced without increasing the size of the accumulator, the reliability can be improved without increasing the manufacturing cost.

Next, the air conditioner 200 of the second embodiment will be described with reference to FIGS. 12 to 15. It should be noted that the points common to the first embodiment will be omitted.
<Conventional expansion valve control when stopped>
FIG. 12 is a refrigeration cycle system diagram showing the conventional expansion valve control at the time of stop applied to the air conditioner 200 for simultaneous cooling and heating. The air conditioner 200 shown here includes an outdoor unit 10, an indoor unit 40 (general term for 40a, 40b, 40c, 40d), and a cooling / heating switching unit 30 (30a, 30b) existing between the indoor unit 40 and the outdoor unit 10. , 30c, 30d) are connected by gas pipes such as the liquid main pipe 21, the high and low pressure gas main pipe 26, and the low pressure gas main pipe 27. It is in the state of stop, cooling stop, and ventilation (low pressure stop). Although FIG. 12 illustrates a configuration in which one outdoor unit 10 and four indoor units 40 are used, a configuration other than this may be used.

One end of the indoor heat exchanger 41 of the indoor unit 40 is connected to the high / low pressure gas main pipe 26 or the low pressure gas main pipe 27 via the cooling / heating switching unit 30, and the other end is connected to the liquid main pipe 21 via the indoor expansion valve 42. There is.

The cooling / heating switching unit 30 is a branch circuit that selectively connects the indoor unit 40 to the high / low pressure gas main pipe 26 or the low pressure gas main pipe 27, and is referred to as an expansion valve 31 for high / low pressure gas pipes 31 (general term for 31a, 31b, 31c, 31d). , A low-pressure gas pipe expansion valve 32 (general term for 32a, 32b, 32c, 32d) is provided. By controlling the opening and closing of the expansion valve 31 for high and low pressure gas pipes and the expansion valve 32 for low pressure gas pipes, the direction of the refrigerant flowing through the indoor unit 40 is changed, and the indoor expansion valves 42 (42a, 42b, 42c, 42d) are generically used. ), The action of the evaporator and the action of the condenser of the indoor heat exchanger 41 (general term for 41a, 41b, 41c, 41d) are switched in cooperation with the depressurization throttle and the opening / closing operation.

The outdoor unit 10 is composed of a compressor 11, a heat exchanger side four-way valve 12a, a high / low pressure gas pipe side four-way valve 12b, an outdoor heat exchanger 14, an outdoor expansion valve 15, and an accumulator 18. One end of the outdoor heat exchanger 14 communicates with the liquid main pipe 21 via the outdoor expansion valve 15, and the other end is the discharge side and the suction side of the compressor 11 by the heat exchanger side four-way valve 12a. Is selectively connected to. Further, the high / low pressure gas main pipe 26 is selectively connected to the discharge side and the suction side of the compressor 11 by the high / low pressure gas pipe side four-way valve 12b. In FIG. 12, both the high / low pressure gas main pipe 26 and the outdoor heat exchanger 14 are connected to the discharge side of the compressor 11, but each of them is connected to the suction side depending on the operating state of the indoor unit 40 and the cooling / heating load ratio. In some cases.

Next, the flow of the refrigerant during operation and during stop will be described. During operation, a part of the high-temperature high-pressure gas refrigerant compressed by the compressor 11 passes through the high-low pressure gas pipe side four-way valve 12b, the high-low pressure gas main pipe 26, and the high-low pressure gas pipe expansion valve 31a of the cooling / heating switching unit 30a. , It is sent to the indoor unit 40a for heating operation. In the indoor unit 40a, the gas refrigerant flowing into the indoor heat exchanger 41a exchanges heat with the indoor air and condenses to become a high-pressure two-phase refrigerant or a high-pressure overcooling refrigerant, which is sent to the indoor expansion valve 42 and the liquid main pipe 21.

The rest of the high-temperature high-pressure gas refrigerant compressed by the compressor 11 is sent to the outdoor heat exchanger 14 via the heat exchanger side four-way valve 12a, exchanges heat with the outdoor air and condenses, and is a high-pressure two-phase refrigerant or high pressure. It becomes an overcooling refrigerant and is sent to the liquid main pipe 21 through the outdoor expansion valve 15.

The liquid refrigerant sent from the indoor unit 40a and the outdoor unit 10 to the liquid main pipe 21 and merged is sent to the indoor unit 40c for cooling operation, the flow rate is adjusted by the indoor expansion valve 42c, and heat exchange with the indoor air by the indoor heat exchanger 41c. Evaporates and becomes a low-pressure gas refrigerant. Then, it is sent to the compressor 11 via the cooling / heating switching unit 30c, the expansion valve 32c for the low-pressure gas pipe, and the low-pressure gas main pipe 27, and the refrigeration cycle is completed. During this operation, the inside of the liquid main pipe 21 is substantially filled with the liquid refrigerant, and only the gas refrigerant is present in the high and low pressure gas main pipe 26 and the low pressure gas main pipe 27.

When shifting to stop from here, as shown in FIG. 12, in the indoor unit 40, the indoor expansion valve 42a for heating stop is open, the indoor expansion valve 42b for continuing to stop is closed, and the indoor expansion valve 42c for cooling stop is closed. The indoor expansion valve 42d for ventilation is closed. Further, in the cooling / heating switching unit 30, the expansion valve 31a for the high / low pressure gas pipe of the cooling / heating switching unit 30a is kept open and the expansion valve 32b for the low pressure gas pipe is kept closed according to the mode during the operation of the indoor unit. The expansion valves 31b, 31c, 31d for high and low pressure gas pipes of the cooling / heating switching units 30b, 30c, 30d are kept closed, and the expansion valves 32b, 32c, 32d for low pressure gas pipes are kept open. Further, in the outdoor unit 10, the outdoor expansion valve 15 is kept open.

Immediately after the compressor 11 is stopped, the pressures of the outdoor heat exchanger 14 and the high / low pressure gas main pipe 26 downstream thereof decrease, and after a certain period of time, they balance with the suction side pressure of the compressor 11. When this balance pressure becomes lower than the pressure of the liquid main pipe 21, the liquid refrigerant in the liquid main pipe 21 moves to the outdoor heat exchanger 14 through the outdoor expansion valve 15, or the indoor expansion valve 42a, the indoor heat exchanger 41a, and the like. By moving to the high / low pressure gas main pipe 26 through the expansion valve 31a for the high / low pressure gas pipe, the refrigerant movement as shown in FIG. 6 occurs. Further, since the heat exchanger side four-way valve 12a and the compressor check valve 16 are not completely sealed, the refrigerant in the outdoor heat exchanger 14 and the high / low pressure gas main pipe 26 may move to the accumulator 18. As described above, if the refrigerant in the liquid main pipe 21 is dispersed in various parts of the refrigeration cycle, the operation efficiency is poor and it takes time to start up until the refrigerant is properly distributed in each part of the refrigeration cycle at the next start-up. In addition, the amount of liquid returned at startup increases, the liquid-refrigerant separation function of the accumulator deteriorates, and the risk of compressor liquid compression increases. To prevent this, it is necessary to increase the accumulator volume, which increases the manufacturing cost.
<Control of expansion valve when stopped in Example 2>
FIG. 13 is a refrigeration cycle system diagram showing the stop expansion valve control of the second embodiment applied to the air conditioner 200 having the same configuration as that of FIG. 12. As shown here, in the stop-time expansion valve control of this embodiment, after the compressor 11 is stopped, all the expansion valves, that is, all of the indoor expansion valves 42, all of the expansion valves 31 for high and low pressure gas pipes, and low pressure gas. All of the expansion valves 32 for pipes and the outdoor expansion valves 15 are closed. As a result, it is possible to prevent the liquid refrigerant accumulated in the liquid main pipe 21 from moving to another place during operation, and it is possible to obtain the same effect as that of the first embodiment even in the air conditioner 200 of the simultaneous cooling / heating multi. can.

FIG. 14 is a modification of the stop expansion valve control of the second embodiment, which is a stop expansion valve control in which all the indoor expansion valves 42 and the outdoor expansion valve 15 are closed after the compressor 11 is stopped. This makes it possible to prevent the liquid refrigerant accumulated in the liquid main pipe 21 from moving to another place during operation. In this modification, since the expansion valve control of the cooling / heating switching unit 30 is not required, it can be easily manufactured as compared with FIG. In this modification, the refrigerant of the indoor heat exchanger 41a in the heating operation moves to the high / low pressure gas main pipe 26 via the expansion valve 31a for the high / low pressure gas pipe, and the refrigerant in the indoor heat exchanger 41c in the cooling operation has a low pressure. Although it moves to the low-pressure gas main pipe 27 via the expansion valve 32c for the gas pipe, since the amount of the moving refrigerant is limited, almost the same effect as in FIG. 13 can be obtained.

FIG. 15 is another modification of the expansion valve control at the time of stop of the second embodiment, and after the compressor 11 is stopped, all of the expansion valves 31 for high and low pressure gas pipes, all of the expansion valves 32 for low pressure gas pipes, and the outdoors. It is an expansion valve control at the time of stopping when all the expansion valves 15 are closed. This makes it possible to prevent the liquid refrigerant accumulated in the liquid main pipe 21 from moving to another place during operation. In this modification, since it is not necessary to control the indoor expansion valve 42, it can be easily manufactured as compared with FIG. Even in this modification, the liquid refrigerant of the liquid main pipe 21 moves to the indoor heat exchanger 41a and the cooling / heating switching unit 30a via the indoor expansion valve 42a of the heating operation, but it is possible to prevent the liquid refrigerant from moving to another place. Therefore, it is possible to obtain almost the same effect as in FIGS. 13 and 14.

Next, the air conditioner of the third embodiment will be described with reference to FIGS. 16 and 17. It should be noted that the points common to the above-described embodiment will be omitted.
<Conventional expansion valve control when stopped>
FIG. 16 is a refrigeration cycle system diagram showing a conventional expansion valve control at a stop, which is applied to an air conditioner 300 of a two-tube type simultaneous cooling / heating multi. The air conditioner 300 shown here includes an outdoor unit 10, an indoor unit 40 (40a, 40b, 40c, 40d), and a cooling / heating switching unit 30 existing between the indoor unit 40 and the outdoor unit 10 together with a high-pressure main pipe 28. The indoor units 40 are connected by a low-pressure main pipe 29, and are in a state of heating high-pressure stop, heating low-pressure stop, cooling stop, and air blowing (low-pressure stop), respectively. Although FIG. 16 shows a configuration in which one outdoor unit 10 and four indoor units 40 are used, the number of units may be other than this.

The cooling / heating switching unit 30 includes a gas-liquid separator 63, a first expansion valve 64, a second expansion valve 65, a high-pressure pipe switching valve 61 (general term for 61a, 61b, 61c, 61d), and a low-pressure pipe switching valve 62 (62a, 62b). , 62c, 62d). One end of the indoor heat exchanger 41 of the indoor unit 40 is connected to the high-pressure pipe switching valve 61 and the low-pressure pipe switching valve 62, and the other end is the lower liquid of the gas-liquid separator 63 via the indoor expansion valve 42. Connected to the pipe. Here, a solenoid valve is used for the high-pressure pipe switching valve 61 and the low-pressure pipe switching valve 62.

Further, the cooling / heating switching unit 30 changes the direction of the refrigerant flowing through the indoor unit 40 by controlling the opening and closing of the high-pressure pipe switching valve 61 and the low-pressure pipe switching valve 62, and reduces the pressure reducing and opening / closing operation of the indoor expansion valve 42. The action of the evaporator and the action of the condenser of the indoor heat exchanger 41 are switched in cooperation with the above.

The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger fan 13, an outdoor heat exchanger 14, an outdoor expansion valve 15, a compressor check valve 16, and an accumulator 18. Then, one end of the outdoor heat exchanger 14 communicates with the high pressure main pipe 28 or the low pressure main pipe 29 via the outdoor expansion valve 15. Which main pipe is communicated depends on the pressure of the outdoor heat exchanger 14. Generally, in the case of high pressure, it is connected to the high pressure main pipe 28, and in the case of low pressure, it is connected to the low pressure main pipe 29.

Next, the flow of the refrigerant during operation and during stop will be described. During operation, the high-temperature high-pressure gas refrigerant compressed by the compressor 11 is sent to the outdoor heat exchanger 14 via the four-way valve 12, exchanges heat with the outdoor air and condenses to become a high-pressure two-phase refrigerant, and becomes an outdoor. It is sent to the high-pressure main pipe 28 and the cooling / heating switching unit 30 through the expansion valve 15 and the check valve. The high-pressure two-phase refrigerant sent to the cooling / heating switching unit 30 is separated into a gas refrigerant and a liquid refrigerant by the gas-liquid separator 63.

A part of the high-pressure gas refrigerant separated by the gas-liquid separator 63 is sent to the indoor unit 40a during heating operation through the high-pressure pipe switching valve 61a, and heat exchanges with the indoor air in the indoor heat exchanger 41a to condense. It becomes a liquid refrigerant. This liquid refrigerant passes through the indoor expansion valve 42a and the check valve, and flows to the lower liquid pipe of the gas-liquid separator 63. Since the pressure of the lower liquid pipe needs to be lower than the pressure of the gas-liquid separator 63, the pressure of the lower liquid pipe is adjusted by controlling the first expansion valve 64 and the second expansion valve 65.

On the other hand, the liquid refrigerant separated by the gas-liquid separator 63 is sent to the liquid pipe through the first expansion valve. The liquid refrigerant sent from the indoor unit 40a and the gas-liquid separator 63 is sent to the indoor unit 40c to be cooled, the flow rate is adjusted by the indoor expansion valve 42c, and the indoor heat exchanger 41c exchanges heat with the indoor air to evaporate. However, it becomes a low-pressure gas refrigerant. This low-pressure gas refrigerant is sent to the outdoor unit 10 via the low-pressure pipe switching valve 62c and the low-pressure main pipe 29.

The low-pressure gas refrigerant sent to the outdoor unit 10 is sent to the compressor 11 via the check valve, the four-way valve 12, and the accumulator 18, and the refrigeration cycle is completed. During this operation, a large amount of liquid refrigerant is present in the high-pressure main pipe 28 and the lower liquid pipe of the gas-liquid separator 63.

When shifting to stop from here, as shown in FIG. 16, in the indoor unit 40, the indoor expansion valve 42a for heating stop is open, the indoor expansion valve 42b for continuing to stop is closed, and the indoor expansion valve 42c for cooling stop is closed. The indoor expansion valve 42d for ventilation is closed. Further, in the cooling / heating switching unit 30, the first expansion valve 64 is opened, the second expansion valve 65 is closed, the high pressure pipe switching valve 61a, and the low pressure pipe switching valve 62b are closed. Further, in the outdoor unit 10, the outdoor expansion valve 15 is kept open.

Immediately after the compressor 11 is stopped, the pressures of the outdoor heat exchanger 14 and the high-pressure main pipe 28 downstream thereof decrease, and after a certain period of time, they balance with the suction side pressure of the compressor 11. Here, since the check valve or the like used in the outdoor unit is not completely sealed, the refrigerant in the outdoor heat exchanger 14 or the high-pressure main pipe 28 may move to the accumulator 18. As described above, if the refrigerant or the like in the high-pressure main pipe 28 is dispersed in various parts of the cycle, the operation efficiency is poor and it takes time to start up until the refrigerant is properly distributed to each part of the refrigeration cycle at the next start-up. In addition, the amount of liquid returned at startup increases, the liquid-refrigerant separation function of the accumulator deteriorates, and the risk of compressor liquid compression increases. To prevent this, it is necessary to increase the accumulator volume, which increases the manufacturing cost.
<Control of expansion valve when stopped in Example 3>
FIG. 17 is a refrigeration cycle system diagram showing the stop expansion valve control of the third embodiment applied to the air conditioner 300 having the same configuration as that of FIG. As shown here, in the stop-time expansion valve control of this embodiment, after the compressor 11 is stopped, all the valves, that is, all of the indoor expansion valves 42, all of the high-pressure pipe switching valves 61, and the low-pressure pipe switching valves 62. All, and the first expansion valve 64, the second expansion valve 65, and the outdoor expansion valve 15 are closed. As a result, it is possible to prevent the liquid refrigerant accumulated in the high-pressure main pipe 28 and the lower liquid pipe of the gas-liquid separator 63 from moving to another place during operation, and in the air conditioner 300 of the two-tube type cooling / heating simultaneous multi. However, the same effect as that of Example 1 can be obtained.

Next, the air conditioner of the fourth embodiment will be described with reference to FIG. It should be noted that the points common to the above-described embodiment will be omitted.

FIG. 18 is an example of using the supercooling heat exchanger 19 during the cooling operation. A part of the high-pressure liquid refrigerant condensed during the cooling operation is used to cool the remaining liquid refrigerant sent into the room. The supercooling expansion valve 20 sends a part of the refrigerant to the supercooling heat exchanger 19, and the remaining liquid. After cooling the refrigerant, it is sent to the suction side of the compressor. In this case, even if the outdoor unit is on the bottom and the indoor unit is on the top due to the height difference construction, the liquid pipe is full even if the pipe length is long and the pressure loss of the liquid pipe is large. Further, depending on the conditions, the temperature can be cooled to a temperature lower than the outside air temperature, so if the expansion valves before and after the liquid pipe are closed as it is, the liquid is sealed. If the temperature of the liquid refrigerant rises due to the outside air, the pressure of the liquid refrigerant may rise.

If the supercooled heat exchanger 19 is used during cooling, the valve should not be closed carelessly. It is recommended to close after the temperature of the liquid pipe rises, or after the refrigerant in the liquid pipe has moved to other equipment to some extent. The pressure and the behavior of the refrigerant movement may be estimated from the temperature and pressure of the liquid pipe during stop.

100, 200, 300, 400 air conditioner,
10 outdoor unit,
11 Compressor,
12 four-way valve,
12a heat exchanger side four-way valve,
12b High / low pressure gas pipe side four-way valve,
13 Outdoor heat exchanger fan,
14 Outdoor heat exchanger,
15 Outdoor expansion valve,
16 Compressor check valve,
18 accumulator,
19 Supercooled heat exchanger,
20 Supercooled expansion valve,
21 liquid main pipe,
24 gas main,
26 High and low pressure gas main,
27 Low pressure gas main,
28 High-pressure main pipe,
29 Low pressure main pipe,
30, 30a, 30b, 30c, 30d cooling / heating switching unit,
31, 31a, 31b, 31c, 31d Expansion valve for high and low pressure gas pipes,
32, 32a, 32b, 32c, 32d Expansion valve for low pressure gas pipe,
40, 40a, 40b, 40c, 40d indoor unit,
41, 41a, 41b, 41c, 41d indoor heat exchanger,
42, 42a, 42b, 42c, 42d indoor expansion valve,
45, 45a, 45b, 45c, 45d Indoor heat exchanger gas temperature sensor,
46, 46a, 46b, 46c, 46d Indoor heat exchanger liquid temperature sensor,
47 Discharge temperature sensor,
49, 49a, 49b, 49c, 49d Indoor heat exchanger fan,
50 Outdoor heat exchanger liquid temperature sensor,
51 Outdoor heat exchanger gas temperature sensor,
52 Liquid tube temperature sensor,
55 Discharge pressure detection sensor,
56 Inhalation pressure detection sensor,
61, 61a, 61b, 61c, 61d switching valve for high pressure pipe,
62, 62a, 62b, 62c, 62d switching valve for low pressure pipe,
63 Gas-liquid separator,
64 First expansion valve,
65 Second expansion valve,
71 Liquid pressure detector,
72 Outside air temperature sensor,
73, 73a, 73b, 73c, 73d Indoor temperature sensor

Claims (7)

A compressor, an outdoor heat exchanger, an outdoor unit with an outdoor expansion valve, and
Indoor heat exchanger, indoor unit with indoor expansion valve,
The liquid pipe connecting the outdoor unit and the indoor unit,
A gas pipe connecting the outdoor unit and the indoor unit,
It is an air conditioner equipped with
One end of the outdoor heat exchanger is connected to the liquid pipe via the outdoor expansion valve.
One end of the indoor heat exchanger is connected to the liquid pipe via the indoor expansion valve.
After a predetermined time has elapsed from the stop of the compressor and the liquid pressure at the initial stop is lowered , both the outdoor expansion valve and the indoor expansion valve are closed , and this closed state is maintained until the next start-up . Characterized air conditioner. A compressor, an outdoor heat exchanger, an outdoor unit with an outdoor expansion valve, and
Indoor heat exchanger, indoor unit with indoor expansion valve,
A cooling / heating switching unit having a high / low pressure gas pipe switching valve and a low pressure gas pipe switching valve,
The liquid pipe connecting the outdoor unit and the indoor unit,
A high-low pressure gas pipe connecting the outdoor unit and the high-low pressure gas pipe switching valve,
A low-pressure gas pipe connecting the outdoor unit and the low-pressure gas pipe switching valve,
A gas pipe connecting the indoor unit and the cooling / heating switching unit,
It is an air conditioner equipped with
One end of the outdoor heat exchanger is connected to the liquid pipe via the outdoor expansion valve.
One end of the indoor heat exchanger is connected to the liquid pipe via the indoor expansion valve.
After a predetermined time has passed since the compressor was stopped and the liquid pressure at the initial stage of the stop was lowered ,
Either close both the outdoor expansion valve and the indoor expansion valve,
An air conditioner characterized in that all of the outdoor expansion valve, the high / low pressure gas pipe switching valve, and the low pressure gas pipe switching valve are closed , and the closed state is maintained until the next start -up. A compressor, an outdoor heat exchanger, an outdoor unit with an outdoor expansion valve, and
Indoor heat exchanger, indoor unit with indoor expansion valve,
A cooling / heating switching unit with a gas-liquid separator, a switching valve for high-pressure pipes, a switching valve for low-pressure pipes, and a hydraulic pressure adjusting valve,
A high-pressure pipe connecting the outdoor unit and the cooling / heating switching unit,
A low-pressure pipe connecting the outdoor unit and the cooling / heating switching unit,
A gas pipe connecting the indoor unit and the cooling / heating switching unit,
A liquid pipe connecting the indoor unit and the cooling / heating switching unit,
It is an air conditioner equipped with
One end of the outdoor heat exchanger is connected to the high pressure pipe via the outdoor expansion valve.
One end of the indoor heat exchanger is connected to the liquid pipe via the indoor expansion valve.
After a predetermined time has passed since the compressor was stopped and the liquid pressure at the initial stage of the stop was lowered ,
The air is characterized in that all of the outdoor expansion valve, the indoor expansion valve, the high pressure pipe switching valve, the low pressure pipe switching valve, and the hydraulic pressure adjusting valve are closed , and this closed state is maintained until the next start-up. Harmony machine. In the air conditioner according to any one of claims 1 to 3, the air conditioner
An air conditioner characterized in that a predetermined valve is closed when the hydraulic pressure in the liquid pipe becomes a predetermined value or less. In the air conditioner according to any one of claims 1 to 3, the air conditioner
An air conditioner characterized in that a predetermined valve is closed when the inside of the liquid pipe is not a liquid seal. In the air conditioner according to any one of claims 1 to 3, the air conditioner
An air conditioner characterized in that when the hydraulic pressure in the liquid pipe rises after closing a predetermined valve, any of the valves is opened. In the air conditioner according to claim 5,
An air conditioner characterized in that the detection of the hydraulic pressure in the liquid pipe is estimated based on the output of a temperature sensor, a pressure sensor installed in the refrigeration cycle process, or an outside air temperature sensor installed in the outdoor unit.

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